Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common neuropsychiatric disorders in childhood and can persist into adulthood. Despite its prevalence, diagnosis remains primarily clinical, and it is based on behavioural observation and standardised questionnaires but with few objective tools to validate diagnoses. The use of electroencephalogram (EEG) has emerged as a potential tool to identify neurophysiological biomarkers of ADHD, and research on EEG-based neurofeedback has shown promising results as a therapeutic intervention. This article reviews recent studies looking at the role of EEG in the assessment and treatment of ADHD, with a focus on key findings, current limitations, and future directions.